Experiments are being conducted to assess the roles of estradiol and progesterone in the regulation of sexual response patterns of female rats during the estrous cyles. The effects of acute ovarian removal at various times during the estrous cycle on lordosis behavior and secretion of luteinizing hormone are being systematically evaluated. Blood levels of estradiol and progesterone throughout the estrous cycle of females housed under our laboratory conditions are being measured to better characterize the hormonal conditions to which experimental females have been exposed prior to acute ovariectomy.